Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/02—Generating seismic energy
  • G01V1/143—Generating seismic energy using mechanical driving means, e.g. motor driven shaft
  • G01V1/147—Generating seismic energy using mechanical driving means, e.g. motor driven shaft using impact of dropping masses

Definitions

• the present invention relates to a pulse energization device for architectural structures.
• the invention inserts in the field of the seismic testing of the architectural structures and, more precisely, it concerns a pulse energization which uses a dynamic load cell and an instrument for the excitation of the structures to be tested.
• this invention refers to a device that allows energizing and the subsequent detection of the frequency spectrum of an existing and operating structure, without the need to evacuate the structure itself, or temporarily block the activities in it provided.
• the term “energizing” means the stress of the structure to be tested, through an instant collision caused by an instrument, which for the sake of convenience will be hereinafter called “energizer”. More in general, the energization consists in the propagation of seismic waves by a source, and is carried out in order to detect these waves by means of receivers, so as to perform the image reconstruction of the stressed structure, through the use of the path time of the seismic waves that propagate through a given section.
• the reference standards are: Ordinance No. 3274 of 20.03.2003 of the President of the Council of Ministers, having title: "First elements about the general criteria for the seismic classification of the national territory and technical standards for buildings in seismic areas", published in the Ordinary Supplement No. 72 of the Official Gazette No. 105 of 05.08.2003, and the 2008 Technical Standards for Construction (NTC 2008 - DM 14/01/2008).
• NTC 2008 - DM 14/01/2008 The knowledge of the seismic vulnerability of these structures is required in the Ordinance, in its subsequent amendments and connected NTC.
• NTC provide, except in specific cases in which the features of the grounds require further experimental controls, the calculation parameters in order to know these external applied forces, the geographical coordinates being known and excluding site exceptions and effects related to the local shape of the ground.
• any structure it is always possible to detect with geophysical methods (for instance detection of the micro-tremors due to tectonic movements) the resonant frequency of the ground on which it stands, the spectrum of ground acceleration and to estimate its natural frequency; once these parameters have been detected, it is easy, together with the parameters characterizing the vibration modes of the structure, to build a model of finite elements calculation (and/or to refine or validate an existing one). While for the grounds it is possible to detect some reliable tomographic measures, estimate of the resonant frequency of the architectural structures through the micro-tremors does not have the required degree of precision for a proper evaluation.
• the dynamic characterization tests are nowadays considered among the most complete and effective survey techniques for understanding the aspects characterizing the behavior of the structure in its life or in case of earthquake. This is mostly true with regard to large structures, such as important buildings, bridges and viaducts.
• the dynamic tests are the instrument that can at best identify the real behavior against the dynamic stresses imposed by anthropic and/or natural external applied forces.
• the first presents the drawback of not having the energy needed to properly excite the structure, both in amplitude and in the various modes of vibration.
• the second method presents the disadvantage of not allowing the high precisions needed for an optimal dynamic characterization. It is not possible, indeed, to reproduce the same stress unless errors in the order of a percentage up to 20%, unacceptable for the type of test needed.
• the third method cannot be disadvantageously applicable on many structures such as bridges or structures in elevation. Even when it can be applied to these structures, it allows a few surveys per day, due to the excessive laboriousness of assembly/disassembly of the equipment.
• the fourth method and fifth method are optimal, but with complex, long and expensive use. Indeed, in order to get the required accuracy, it is necessary to stop traffic and/or evacuate the structure, make some very deep holes in the structure in order to fix the instruments to it, performing the energization and take the measures, then disassemble the instruments and provide to restore normal provided activity, previously stopped.
• the sixth method consists of a hammer provided with a detection instrument of the waves propagated in the structure. It must be directly driven by an operator, who must hit the structure at the highest speed as possible. Of course, the higher the weight of the instrument, the more effective is the energization stroke. On the other hand, a high weight is hard to move and is also dangerous for the operator itself. For these reasons, therefore, instrumented hammers weighing more than 5-7 Kg do not exist. This method, therefore, even if optimal, can be disadvantageously used only on light structures, which can be stressed by the weak forces of a hammer weighing at most a few kilos.
• the present invention inserts in this general research outline of getting the best technical features for performing an optimal seismic test, intended to achieve efficiency and reliability features in an energization device, whose structure, thus, presents technical and functional advantages.
• the purpose of the present invention is to propose an energization device, able to apply a pulse external applied force of several thousand of kilos and measure the seismic response of the structure to which it is applied, through a dynamic load cell.
• Another purpose of the present invention is to create a new energization device suitable to perform the dynamic analysis through the
• Further purpose of the present invention is to achieve a method of seismic test of buildings using a pulse energization device more reliable and cheaper than those ones which use the instruments of the known technique.
• Another purpose of the present invention is to provide a energization device that ca be easily transportable.
• purpose of the present invention is to define an energization device that can be used even during the progress of the normal activities provided on/in the structure to be tested.
• purpose of the present invention is to design an energization device that allows in a short time to repeat the test on the whole structure, allowing the repeatability thereof necessary for a precise diagnosis of the degradation of the structures.
• a pulse energization device for architectural structures is, therefore, object of the present invention.
• the device according to the present invention allows the use of existing instruments in an intelligent manner, eliminating all the drawbacks due to their use.
• Another advantage of the present invention is the possibility to perform an accurate test of the architectural structures that need it, causing minimal interferences in respect of the activities which usually take place inside or on the structures themselves.
• the easy repeatability of the test makes the device object of the invention useful for systematic controls over time.
• FIG. 1 is a three-dimensional schematic view of the device according to the invention.
• FIG. 2 is a schematic longitudinal section of the device of figure 1 , on which a first embodiment of energizer is applied;
• figure 3 is a detail of the section of figure 2, according to the present invention.
• figure 4 is an overall view of the device of figure 1 , on which the energizer shown in figure 2 is applied, according to the invention.
• the device 1 comprises a first base plate 2 and a second base plate 3, between which there is a load cell 4.
• Four guide elements 5, reciprocally connected, at their top, by a third end-of-stroke plate 6 are mounted on the first base plate 2.
• the second base plate 3 presents holes 7, in order to be free to slide along the guide elements 5.
• the guide elements 5 are made of plastic material, so as to advantageously avoid distorting force data measured by the cell.
• An energizer 8, in particular a blaster, free to slide along the guide elements 5, is provided above the second plate 3.
• a circular plate 9, fixed with screw pins, is provided above the energizer 8.
• Known blasters, of the type shown in the attached drawings have the drawback of presenting two locking pins of the explosive trigger, that bend easily; advantageously, the fastening with the screw pins is able to make up for this defect.
• the device 1 is placed in contrast to a mass resting on the ground, in order to stress structures even with horizontal external applied forces (houses, bridges piers, etc.).
• centering means 9 for the guide elements 5 are present inside the holes 7 of the second base plate.
• these centering means 9 are made of teflon or nylon.
• the first and second plate 2, 3 are separated by spacers 10 having a height lower than the height of the cell 4, to which cell 4 the second base plate 3 is bound through hooking means 11 that make them integral in the movements along the guide elements 5.
• the lower surface of the first plate 2 and the upper surface of the second plate 3 are covered with a coating material 12, for instance rubber or neoprene, preferably with high density, suitable to absorb the stroke and consequent vibrations caused by the energizer 8, and to the uniform and gradual distribution of these vibrations on the load cell 4 and structure to be tested (not shown).
• the energizer 8 when the energizer 8 is operated, it causes a stroke with the second base plate 3, which transmits the vibrations to the load cell 4. As a consequence of the stroke, the energizer 8 is free to slide along the guide elements 5. Given the energy released, the guide elements 5 advantageously prevent uncontrolled movements of the energizer 8 which otherwise might even dangerously hit the operators assigned to the measure or passing through the work area.
• the guide elements 5 allow a proper positioning of the energizer 8 with respect to the load cell 4, so that the vibrations are optimally detected.
• locking means are provided on the third plate 6, in order to block the energizer 8 on account of the stroke and subsequent bounce towards the third plate 6 itself. In this way, the energizer remains locked above and cannot fall again on the second base plate 3, causing a second stroke. Although the vibrations caused by the second stroke however provoke a negligible error compared to those ones detected by the known devices, these locking means allow to detect a cleaner signal.
• the energizer consists of a sphere, or object in other shape, suitable to slide along the guide elements 5, made of a material having a high specific weight.
• the energizer in its rest position is fixed to the top of the guide elements 5, at the lower surface of the third plate 6. Upon its activation, it is left to fall freely, its movement being precisely controlled by the guide elements 5. Once the stroke has been occurred, whose waves are detected similarly to the embodiment described above, the energizer bounces back and remains bound to the locking means, so as not to cause interferences to the signal detected.
• the structure is mounted horizontally, on a sheet.
• a sheet presents on the contact surface to the structure a coating made of a material suitable to absorb the stroke and gradually transfer it to the structure, such as for instance rubber or neoprene; on the opposite surface, instead, it presents some end-of- stroke elements that prevent, at the operation of the energizer, the horizontal movement of the device, due to the shock wave.

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• Engineering & Computer Science (AREA)
• Remote Sensing (AREA)
• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Acoustics & Sound (AREA)
• Environmental & Geological Engineering (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Geophysics And Detection Of Objects (AREA)
• Roof Covering Using Slabs Or Stiff Sheets (AREA)

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Citations (5)

• 2010
  • 2010-08-05 IT ITVI2010A000227A patent/IT1401399B1/it active
• 2011
  • 2011-08-02 WO PCT/IT2011/000279 patent/WO2012017467A1/en active Application Filing

Patent Citations (5)

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